Fractional skin treatment is a relatively new skin treatment technique. The treatment is performed by application to the skin of a plurality of focused laser beams. The beams are organized into one or two dimensional arrays. The plurality of laser beams affects a corresponding number of skin locations and forms microscopic columns of treated skin spots or areas. The treated skin areas are surrounded by untreated skin areas. The treated skin areas that could be micro-lesions are scattered over the skin and support a faster skin healing than if the entire area was treated. Fractional skin treatment has certain benefits over conventional laser skin treatment and the approach is gaining popularity in the market.
Different types of beam splitters are used to generate a plurality of laser beams from a single laser beam. One of the types of beam splitters is a Diffractive Beam Splitter. Diffractive optical element (DOE) and in particular diffractive beam splitters are periodic phase structures that split the input laser beam into multiple diffractive orders or beamlets, while retaining the divergence angle, diameter and polarization of the input beam.
These beamlets are characterized by an equal intensity and equal angle to one another. There are both one-dimensional and two-dimensional (1D/2D) diffractive beam splitting elements. 1D elements split beams along a straight line whereas 2D elements produce beams arranged in a matrix of, for example, 2×2 or 6×6 spots.
Usually, a lens is placed after such element as a diffractive beam splitter and the focused array or matrix of laser spots will appear in the focal plane of the lens. The distance or pitch between the spots in the focal plane depends on the working distance of the lens and the separation angle that is determined during the design of the DOE.
The following US patents and patent application Publications describe different uses of DOE for dermatological skin treatments: U.S. Pat. Nos. 7,072,045; 8,289,603; 8,915,907; 9,247,995; 9,259,594; 9,326,748.
The columns of injury induced by the fractional laser treatment can range from gentle photothermal or photochemical events designed to change one or more functions in tissue, to more intense photothermal events coagulating and or ablating cones of tissue causing a wound healing response with the goal of promoting neocollagenesis and neoelastogenesis. Strongly focused picosecond pulses can also lead to subsurface coagulative or ablative zones inducing a wound healing response without damaging the protective outer skin layers. Both neocollagenesis and neoelastogenesis leads to an improvement in the appearance of wrinkles and fine lines commonly known as rhytides. Fractional laser treatments with diffractive beamsplitters are well verse for generating finite zones of injuries promoting neocollagenesis and neoelastogenesis.